Conventional test elements include a support, usually made of a plastic material or paper that bears a detection layer with detection reagents, which effect a detection reaction when exposed to an analyte such as, for example, glucose or lactate. In detection reactions for photometric determination of an analyte concentration, it is advantageous to spread a body fluid sample, such as blood, on and/or in the detection layer as much as possible. For this reason, it is customary to apply a spreading layer onto the detection layer to facilitate spread of a body fluid sample droplet that has been applied.
For acceptable spreading behavior of the body fluid droplet, the spreading layer has a hydrophilic surface. Likewise, the spreading layer needs to be characterized by a high permeability (i.e., needs to be porous) to allow the body fluid droplet to easily reach the detection layer situated below the spreading layer.
Spreading layers made of fibrous material exhibit desired properties in this context. One disadvantage of fibrous spreading layers, however, is that the requisite manufacturing effort is high to prevent significant variation of the spreading behavior. This disadvantage can be largely circumvented by laminating a porous plastic membrane onto the detection layer to serve as the spreading layer. Such a test element is disclosed in, for example, US Patent Application Publication No. 2005/0186109.
Laminating, however, has its own disadvantages. Most notably, it induces a mechanical stress upon the detection layer and support of the test element. This mechanical stress can cause damage to the resulting test element.
As such, there is a need for additional methods for producing test elements having spreading layers.